Examine source code of GTM Variable Builder

{
  "manifest_version": 2,
  "name": "GTM Variable Builder",
  "description": "From Chrome Developer Console, highlight elements to get JavaScript code. Built by: Triangle Digital (Triangledigital.xyz)",
  "version": "3.8",
  "icons": {
    "128": "icon.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "content_scripts": [
    {
      "matches": [
        "http://*/*",
        "https://*/*"
      ],
      "js": [
        "content_script.js"
      ]
    }
  ],
  "permissions": [
    "activeTab",
    "storage"
  ],
  "optional_permissions": [
    "tabs",
    "alarms",
    "webRequest",
    "webNavigation",
    "scripting"
  ],
  "host_permissions": [
    "<all_urls>"
  ],
  "browser_action": {
    "default_title": "Enable Remarketing Selector",
    "default_icon": "icon.png",
    "default_popup": "popup/popup.html"
  },
  "web_accessible_resources": [
    "safe-browsing-notification/index.html"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{62248867-f8ad-44d6-900a-cd07fc0e276e}"
    }
  }
}